@CHARSET "UTF-8";
.mydiv{width: 70%;margin: 20px auto;}
        ul{
            list-style: none;overflow: hidden;
        }
        #nav{
            width: 400px;height: 40px;text-align: center;line-height: 40px;
            background: #c5c5c5;
        }
        #nav li{
            width: 25%;height: 40px;float: left;border: 1px solid #c5c5c5;
            border-bottom: none;
        }
        #nav li.active{
            background: #fff;
        }
        #content{
            width: 400px;height: 300px;position: relative;border: 1px solid #c5c5c5;border-top: none;
        }
        #content li{width: 100%;height: 100%;position: absolute;padding: 10px;display: none}
  